The present invention relates to a compressor and more particularly to a compressor provided with a pressure relief valve.
A piston type compressor such as a swash plate type compressor, generally, includes a suction chamber and a discharge chamber defined in a housing, and a cylinder block which is provided with a plurality of cylinder bores. The cylinder bores are each arranged to correspond to the suction chamber and the discharge chamber through a valve plate assembly. A piston is slidably disposed in each of the cylinder bores. During reciprocating movement of the piston, refrigerant in the suction chamber is drawn into each of the cylinder bores and the refrigerant in the cylinder bores are compressed and discharged into the discharge chamber.
Therefore, while the compressor is driven, the refrigerant in the discharge chamber becomes high in pressure and the refrigerant in the suction chamber becomes low in pressure. To lower the pressure of the refrigerant in the discharge chamber which has become extraordinarily high beyond a predetermined value, a compressor provided with a pressure relief valve is disclosed in Unexamined Japanese Patent Publication No. 9-60588.
When a compressor is provided with a pressure relief valve, the compressor operates safely since the pressure of refrigerant in a discharge chamber which has become extraordinarily high is lowered. If carbon dioxide is applied as refrigerant, refrigerant in the suction chamber as well as refrigerant in the discharge chamber becomes high in pressure. In this case, it is required that the pressure of the refrigerant in the suction chamber is also monitored.
When the discharge chamber and the suction chamber are each provided with a pressure relief valve, however, the pressure relief valves which are different from each other are required since the refrigerant in the discharge chamber is higher in pressure than the refrigerant in the suction chamber. This increases manufacturing cost.
The present invention addresses a compressor in which pressure of refrigerant in a discharge chamber and a suction chamber are monitored at low cost.
To achieve the above object, the present invention has following features. A compressor has a high-pressure relief valve and a low-pressure relief valve. The high-pressure relief valve in use for a discharge region opens when the pressure of gas in the discharge region is more than a first predetermined pressure. The high-pressure relief valve is provided with a first shim. The low-pressure relief valve in use for a suction region opens when the pressure of gas in the suction region is more than a second predetermined pressure which is lower than the first predetermined pressure. The low-pressure relief valve is provided with a second shim. The high-pressure relief valve and the low-pressure relief valve have similar structure to each other.